The present invention relates to a method for determining pressure loss of a pneumatic vehicle tire on a driven axle of a motorized vehicle in which the rotational velocity of the wheels is measured and based on the rotational velocity slip values for the driven wheels are calculated. The invention further refers to a device for performing this method.
There is a considerable need to have an automatic warning for the driver of the vehicle in case the vehicle tires lose pressure. The pressure loss is often a precondition for a tire blowup which, especially for driven wheels, can have catastrophic consequences.
From European documents 0 441 599 and 0 441 600 it is known to measure and evaluate the rotational velocity of the tires. The measured value for the rotational velocity of the tires is already present for vehicles that have an automatic anti-blocking system (ABS) due to the presence of the ABS sensors. The basic principle of the known method is that due to pressure loss the rolling radius of the tire is reduced so that the corresponding wheel must turn faster. In order to prevent false warning signals when maneuvering a curve, the rotational velocities of the diagonally positioned wheels are determined. When the resulting measured average value deviates from the average value of all four rotational velocities by more than 0.1%, a warning signal is produced. However, the known methods are problematic in that only a very small measurable effect is present because the rolling radius of the tire even for a considerable pressure loss is only very small; for example, for a pressure loss of 0.5 bar the rolling radius changes by 1 mm.
It is furthermore known to provide pressure sensors within the wheel rim of the vehicle for monitoring the tire pressure. This requires, on the one hand, special sensors. On the other hand, the sensors must be positioned on rotating parts resulting in a considerable expenditure for such a warning device.
It is therefore an object of the present invention to provide a method and a device for determining the pressure loss of a tire with simple means and with a distinctly measurable effect.